A storage tier is a collection of different types of storage media. Each storage media in the storage tier may have different characteristics that include speed, throughput, size, cost, performance, etc. Various forms of storage tiers are used across the field of computer technology to reduce total storage costs, improve performance, and/or as a requirement of performing certain tasks. The storage media found in a storage tier, depending on the type of storage tier, may include, for example, cache memory, random access memory, solid state drives, hard disk drives, tape drives, local memory, network or cloud storage (e.g., a web server).
Caching is used to store certain data so that subsequent requests for that data may be served faster or more efficiently. In particular, the data may be stored in a cache or cache memory, which may be implemented in hardware, software, or a combination. The cache memory is typically faster or more efficient to retrieve data from than other components in a storage tier. When a requestor (e.g., a cache client) requests data, it may first check the cache for the data. If the data is in the cache (a situation known as a cache hit), the data in the cache is retrieved and provided to the requestor. If the data is not in the cache (a situation known as a cache miss), the requestor retrieves the data from another storage media in the storage tier and stores the retrieved data in the cache for subsequent requests.